1. Field of the Invention
This invention relates to a printing hammer drive mechanism for a printing apparatus capable of printing letters, numbers and symbols by striking types arranged on a printing element, such as type wheel, with a printing hammer.
2. Description of Prior Art
A printing apparatus, often requires the change of printing pressure according to the number of copies desired. In a conventional printing apparatus, it usually the case that printing pressure is changed by changing the force of the spring normally holding the hammer in its rest position. However, the adjustment of printing pressure by adjusting the spring force does not produce accurate and correct amount of printing pressure in most cases.